530 TEE POPULAR SCIENCE MONTHLY 



of Kellogg and Bell.^^ They decide against natural selection, but their 

 evidence for the lady beetle, Hippodamia convergens, can not be re- 

 garded as conclusive since they have made no direct comparison of 

 eliminated and surviving individuals. Their case for the honey bee 

 where observations are made upon free flying individuals and those 

 which have not yet left the shelter of the hive, is much better, but even 

 here I must feel that their numbers are too small to give finally con- 

 clusive results in a problem so difficult as that of natural selection. 

 Furthermore, they suggest that the more abnormal individuals may be 

 made way with before they have the opportunity of leaving the hive. 



A most suggestive result was obtained by Schuster in an investiga- 

 tion of deep and shallow water crabs of the genus Eupagurus}^ He 

 finds that for both sexes, but especially for the males,^* the individuals 

 from deep water were more variable than those from shallow water.^' 

 Schuster wisely leaves the determination of the reason for this differ- 

 ence in variability to the time when more data, and data collected under 

 the guidance of this first study, shall be available. He points out, how- 

 ever, that if these differences in variability are not those of deep water 

 and shallow water local races, but arise anew in each generation, they 

 must be due either to the direct influence of the environment or to 

 selection. If elimination be the true explanation the less variable shal- 

 low-water forms would be regarded as a selection from the more vari- 

 able deep-water population. 



Turning again to studies carried out primarily to test the possible 

 action of natural selection, we may mention the work of Browne on the 

 medusa, Aurelia aurita^^ In this jelly fish the number of marginal 

 sense organs, tentaculocysts, is definitely fixed in the larval stage com- 

 monly known as the Ephyra, and by a comparison of collections of 

 Eph)Tae and adults it is possible to determine whether variation in the 

 number of the marginal sense organs affects the chance of survival 

 from larval to adult life. Since all of the young and adult populations 

 compared were sensibly identical, one must conclude that neither an 

 increase nor a decrease in the number of tentaculocysts is so injurious 

 that there is any selective elimination during development. 



Crampton's study of pupal and pupal-imaginal elimination in the 



"Kellogg, V. L., and Ruby G. Bell, "Studies of Variation in Insects," 

 Proc. Wash. Acad. Sci., Vol. VI., pp. 203-332, 81 figures, 1904. 



" Schuster, E. H. J., ' ' Variation in Eupagurus prideauxi, ' ' Biometrika, Vol. 

 II., pp. 191-210, 1903. 



"Deep water forms were those taken at a depth more than 35 meters; shal- 

 low water forms from a depth of less than 35 meters. 



^ The males are more variable than the females, in both deep and shallow 

 water. 



"Browne, E. T., "Variation in Aurelia aurita," Biometrika, Vol. I., pp. 

 90-108, 1901. 



